Conventional methods of sharpening ice skates involve the clamping of the skate blade horizontally to a skate holder, the base of which is provided with a horizontal face of substantial proportions to facilitate sliding engagement with the horizontal worktable of the grinding machine. The actual operation of grinding the blade involves the manual sliding of the skate holder both longitudinally and transversely while maintaining the blade in contact with the periphery of a grinding wheel.
Because of the non-uniform friction at the interface between the sliding skate holder and the worktable, the ability to hold the skate sensitively in contact with the wheel and at the same time maintain constant cutting velocity, in order to effect uniform removal of metal from the blade, is either impossible or requires extreme care and skill. The situation is complicated by the substantial mass of the skate holder interacting with the slip-stick characteristics of the large frictional interface between skate holder and worktable. The presence of abrasive grinding wheel particles in and upon the surface of the worktable and skate holder not only wear and abrade these surfaces but also embed into them and exacerbates the frictional problem. The fact that normally neither surface is hardened is further contributory to this shortcoming. Attempts to use a low friction surfacing to the underside of the skate holder offers temporary relief from this problem but this eventually becomes embedded with grinding paricles and quickly loses its advantages. Neither is the use of oil advantageous, since it retains grinding particles and quickly degenerates into a lapping compound. As a consequence of these shortcomings of current technology skate grinding machines, and particularly the lack of sensitive control over depth of cut and grinding velocity, a skate's original rocker profile is frequently damaged or destroyed or flat portions or flats are introduced, all of which seriously degrade the skate's and the skater's performance.
In addition it is often difficult to achieve the high degree of surface finish and absence of edge "drag" demanded by exacting skaters, without resorting to subsequent hand polishing operations. Not only are these subsequent polishing operations time consuming but they often degrade the keenness of the edge that should have resulted from the sharpening process. Thus the skater does not receive the maximum benefit that he should from the process. In view of the high probability of receiving an unsatisfactory sharpening, many skaters tend to delay having their skates sharpened, preferring to skate on dull edges of the correct profile rather than run the risk of having expensive skates irretrievably damaged. As a result, the proper performance potential of the skate is not being realized.
Another ice skate sharpening concept is that shown in U.S. Pat. No. 1,480,422 intended for the type of skate typical of the period, having a substantially flat, unrockered blade with "curved end portions". In this, the skate-holder or table is longitudinally guided in a manner resembling the invention claimed herein. It will also be noted that a rotary motion about this longitudinal guide is also involved. Such motion however involves an entirely different function from that claimed in this invention, that of controlling skate height; an adjusting screw being provided to facilitate this. Thus, throughout the course of longitudinal travel no radial motion about the longitudinal axis is involved. This rotary action also enabled the skate to be presented and withdrawn to and from the grinding wheel but in no way did it influence the depth of cut. Hence, with the table properly clamped (tightening "Thumb nut 34") the mechanism provided the flat unrockered contour required for the type and vintage of skate involved.
A severe drawback of this concept is the inability to precisely align the blade with the longitudinal guideway. Also the crude method of adjusting the depth of cut is very inadequate when considered in the knowledge that only a few ten thousandths of an inch should be removed during the final grinding processes. Furthermore the concept does not cater to the modern fully rockered blade contour. A fundamental prerequisite for the production of fine surface finishes by rotary cutting means is the selection of the correct type of grinding or cutting wheel used in conjunction with a properly designed bearing arrangement for the wheel spindle. The foregoing shortcomings pertain to situations where wheel and bearing arrangements are totally satisfactory. Satisfactory performance of the disclosed invention is likewise predicated upon the use of properly designed cutting wheel bearings and the correct type of grinding or cutting wheel.
It is also observed that the grinding wheel shown in the accompanying figures, with a profiled periphery for producing the essential "hollow ground" blade surface, though conventional, is not essential to the invention, any other form of abrading means could be adopted. The term cutting wheel will henceforth be adopted in this specification. In regard to the profile of the "hollow grind", this is customarily of circular form since it is almost invariably formed by a diamond pivoting on centers. In the case of the present invention a circular profile to the cutting wheel periphery is essential, as will be explained later. The means of achieving this profile is not further discussed or illustrated since it is merely an incidental feature. However the radius of curvature does need to be adjustable to accommodate the preferences of different classes of skaters and their personal preferences.